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Functional hydrogels [Elektronische Ressource] / vorgelegt von Robert Fokko Roskamp

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Functional HydrogelsDissertationzur Erlangung des GradesDoktor der NaturwissenschaftenimFachbereich Chemie, Pharmazie und Geowissenschaftender Johannes Gutenberg Universität Mainzvorgelegt vonRobert Fokko Roskampgeboren in Bad SchwalbachMainz, im Juli 2009Die vorliegende Arbeit wurde amMax Plank Institut für Polymerforschung in Mainz, amIESL FORTH in Heraklion und amIan Wark Research Institute in Adelaideunter Anleitung vonProf. Dr. , Prof. Dr. und Dr.in der Zeit von Juli 2006 bis Juli 2009 angefertigt.Dekan: Prof. Dr.1. Berichterstatter: Prof. Dr.2. Prof. Dr.Übrige Mitglieder der Prüfungskommission: Prof. Dr.Prof. Dr.Tag der mündlichen Prüfung: 03. September 2009AbstractHydrogels are used in a variety of applications in daily life, such as super ab sorbers, contact lenses and in drug delivery. Functional hydrogels that allowthe incorporation of additional functionalities have enormous potential for futuredevelopment. The properties of such hydrogels can be diversified by introduc ing responsiveness to external stimuli. These crosslinked polymers are knownto respond to changes in temperature, pH and pressure, as well as chemical andelectrical stimuli, magnetic fields and irradiation. From this responsive behaviorpossible applications arise in many fields like drug delivery, tissue engineering,purification and implementation as actuators, biosensors or for medical coatings.

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Published 01 January 2009
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Functional Hydrogels
Dissertation
zur Erlangung des Grades
Doktor der Naturwissenschaften
im
Fachbereich Chemie, Pharmazie und Geowissenschaften
der Johannes Gutenberg Universität Mainz
vorgelegt von
Robert Fokko Roskamp
geboren in Bad Schwalbach
Mainz, im Juli 2009Die vorliegende Arbeit wurde am
Max Plank Institut für Polymerforschung in Mainz, am
IESL FORTH in Heraklion und am
Ian Wark Research Institute in Adelaide
unter Anleitung von
Prof. Dr. , Prof. Dr. und Dr.
in der Zeit von Juli 2006 bis Juli 2009 angefertigt.
Dekan: Prof. Dr.
1. Berichterstatter: Prof. Dr.
2. Prof. Dr.
Übrige Mitglieder der Prüfungskommission: Prof. Dr.
Prof. Dr.
Tag der mündlichen Prüfung: 03. September 2009Abstract
Hydrogels are used in a variety of applications in daily life, such as super ab
sorbers, contact lenses and in drug delivery. Functional hydrogels that allow
the incorporation of additional functionalities have enormous potential for future
development. The properties of such hydrogels can be diversified by introduc
ing responsiveness to external stimuli. These crosslinked polymers are known
to respond to changes in temperature, pH and pressure, as well as chemical and
electrical stimuli, magnetic fields and irradiation. From this responsive behavior
possible applications arise in many fields like drug delivery, tissue engineering,
purification and implementation as actuators, biosensors or for medical coatings.
However, their interaction with biomaterial and way of functioning are yet not
fully understood.
Therefore, thorough investigations regarding their optical, mechanical and chem
ical nature have to be conducted.
A UV crosslinkable polymer, consisting of N isopropylacrylamide, methacrylic
acid and the UV crosslinker 4 benzoylphenyl methacrylate was synthesized. Its
composition, determined by a comprehensive NMR study, is equivalent to the
composition of the monomer mixture. The chemical characteristics were pre
served during the subsequently formation of hydrogel films by photo crosslink
ing as proved by XPS. For the optical characterization, e.g. the degree of swelling
of very thin films, the spectroscopy of coupled long range surface plasmons is in
troduced. Thicker films, able to guide light waves were analyzed with combined
surface plasmon and optical waveguide mode spectroscopy (SPR/OWS). The
evaluation of the data was facilitated by the reverse Wentzel Kramers Brillouin
(WKB) approximation.
The mesh size and proper motion of the surface anchored hydrogels were inves
tigated by fluorescence correlation spectroscopy (FCS), micro photon correlation
spectroscopy („PCS) and SPR/OWS. The studied gels exhibit a mesh size that
allowed for the diffusion of small biomolecules inside their network. For future
enhancement of probing diffusants, a dye that enables FRET in FCS was immobi
lized in the gel and the diffusion of gold nanoparticles embedded in the polymer
solution was studied by PCS.
iAbstract
These properties can be conveniently tuned by the crosslinking density, which de
pends on the irradiation dose. Additionally, protocols and components for poly
mer analogous reactions based on active ester chemistry of the hydrogel were
developed.
Based on these syntheses and investigations, the hydrogel films are applied in the
fields of medical coatings as well as in biosensing as matrix and biomimetic cush
ion. Their non adhesive properties were proved in cell experiments, SPR/OWS
and ToF SIMS studies. The functionality and nonfouling property of the prepared
hydrogels allowed for adaption to the needs of the respective application.
iiContents
Abstract i
1 Introduction 1
1.1 Hydrogels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.1 Responsive Hydrogels . . . . . . . . . . . . . . . . . . . . . . 2
1.1.2 Functional Hydrogels . . . . . . . . . . . . . . . . . . . . . . 6
1.1.3 PNIPAAm based Hydrogels . . . . . . . . . . . . . . . . . . 7
1.2 Biosensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3 Bio Compatibility and Non Fouling . . . . . . . . . . . . . . . . . . 9
1.4 Aim and Outline of the Thesis . . . . . . . . . . . . . . . . . . . . . . 12
2 Methods 15
2.1 Contact Angle Measurement . . . . . . . . . . . . . . . . . . . . . . . 15
2.2 Surface Plasmon Resonance Spectroscopy (SPR) . . . . . . . . . . . 16
2.3 Optical Waveguide Mode Spectroscopy (OWS) . . . . . . . . . . . . 22
2.3.1 Wentzel Kramers Brillouin (WKB) Approximation . . . . . 24
2.4 Correlation Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.4.1 Fluorescence Correlation Spectroscopy (FCS) . . . . . . . . . 27
2.4.2 Photon Correlation Spectroscopy (PCS) . . . . . . . . . . . . 29
2.5 X ray Photoelectron Spectroscopy (XPS) . . . . . . . . . . . . . . . . 30
2.6 Time of Flight Secondary Ion Mass Spectrometry (ToF SIMS) . . . . 31
2.7 Electrochemical Impedance Spectroscopy (EIS) . . . . . . . . . . . . 32
3 Preparation of the Hydrogel 37
3.1 Polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.2 Grafting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.3 Crosslinking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
3.4 Chemical Modification . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.5 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
vContents
3.6 Experimental Part . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.6.1 P(NIPAAm stat MAA stat MABP) . . . . . . . . . . . . . . . 44
3.6.2 BP silane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.6.3 Active Esters . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
3.6.3.1 TFA NHS . . . . . . . . . . . . . . . . . . . . . . . . 46
3.6.3.2 TFA AO . . . . . . . . . . . . . . . . . . . . . . . . . 46
3.6.3.3 TFA TFPS . . . . . . . . . . . . . . . . . . . . . . . . 46
3.6.3.4 TFA DMPS . . . . . . . . . . . . . . . . . . . . . . . 47
3.6.4 Aminomethylbenzophenone . . . . . . . . . . . . . . . . . . 48
3.6.5 Benzophenylacrylamide . . . . . . . . . . . . . . . . . . . . . 49
4 Chemical Characterization 51
4.1 Polymer Composition by NMR . . . . . . . . . . . . . . . . . . . . . 51
4.2 Hydrogel Surface Chemistry by XPS . . . . . . . . . . . . . . . . . . 53
4.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4.4 Experimental Part . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
5 Optical Characterization 57
5.1 Coupled Long Range Surface Plasmon (cLRSP) Spectroscopy . . . . 58
5.1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
5.1.2 Thin Hydrogel Layers and Diffusion of BSA . . . . . . . . . 59
5.1.3 Conclusion and Outlook . . . . . . . . . . . . . . . . . . . . . 62
5.1.4 Experimental Part . . . . . . . . . . . . . . . . . . . . . . . . 63
5.2 WKB assisted SPR/OWS . . . . . . . . . . . . . . . . . . . . . . . . . 64
5.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
5.2.2 Gradient Fitting . . . . . . . . . . . . . . . . . . . . . . . . . . 64
5.2.3 Conclusion and Outlook . . . . . . . . . . . . . . . . . . . . . 67
5.2.4 Experimental Part . . . . . . . . . . . . . . . . . . . . . . . . 67
6 Dynamic Characterization 69
6.1 Tracking Probe Diffusion . . . . . . . . . . . . . . . . . . . . . . . . . 69
6.1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
6.1.2 FCS of Rhodamine 6G Diffusion . . . . . . . . . . . . . . . . 70
6.1.2.1 Diffusion in the Free Polymer . . . . . . . . . . . . 71
6.1.2.2 Diffusion in the Crosslinked Hydrogel . . . . . . . 74
6.1.3 FRET excited FCS . . . . . . . . . . . . . . . . . . . . . . . . . 76
6.1.4 PCS of embedded Gold Nanoparticles . . . . . . . . . . . . . 78
6.1.5 WKB assisted SPR/OWS of Polymer Diffusion . . . . . . . . 84
vi